Effects of Activated-carbon-supported Nickel on Catalytic Transfer Hydrogenation of Cellulose to Hydrocarbons in a Straight-chain Aliphatic Hydrocarbon Solvent
Kentaro KIMURA, Yusuke KAKUTA, Takeo ONO, Kiyofumi KURIHARA
Catalytic hydrogenation of cellulose in a straight-chain aliphatic hydrocarbon solvent for converting cellulose to hydrocarbons was investigated. Thermally stable hydrocarbon solvents suppress condensation reactions unlike hydrogen-donor solvents, such as alcohol. In addition, hydrogen transfer from a hydrocarbon solvent to cellulose derived oxygenates is possible when the solvent is used with a hydrogenation catalyst, such as palladium on activated carbon (Pd/C). Moreover, cellulose-derived oil (bio-oil) can be directly used as a transportation fuel without removing the solvent. Although the bio-oil yield is high, the use of Pd/C increases the production cost. Therefore, nickel on activated carbon (Ni/C) was employed as a low-cost catalyst in this study to investigate catalytic hydrogenation of cellulose. In the Ni/C-containing solvent, the cleavage of the C–O bond in cellulose was promoted, resulting in the production of levoglucosan and 5-hydroxymethylfurfural. Similar to Pd/C, the use of Ni/C led to hydrogen transfer from the solvent to oxygenates at >300 °C and the production of cellulose-derived hydrocarbons. However, the hydrocarbon yield decreased when the reaction occurred at 400 °C because the reaction products over-decomposed to hydrocarbon gas and polymerized to heavy oil. Therefore, a reaction temperature of 350 °C was noted to favor the production of cellulose-derived hydrocarbons.